Inching closer to finalizing plans for a proposed major league ballpark in downtown San Jose, the city Planning Commission will make a key vote tonight on whether to certify a revised environmental impact report related to the project site.

City redevelopment officials have said land for the ballpark and at least one phase of an improved roadway would cost taxpayers $72 million, while a second, $11 million phase could be paid by federal funds. But the latest report lays out a few other scenarios.

Building giant parking structures — which critics insist are necessary to accommodate baseball fans — and acquiring additional properties that might be needed for parking or for widening more of the main roadway to the stadium site would cost millions more, downtown real estate experts say.

And that doesn’t even include a string of properties along the east side of Autumn Street, from Park Avenue to Santa Clara Street, that city officials say may ultimately be acquired for further widening of that roadway or for park land along the Los Gatos Creek Trail. Both options have been planned for years as elements of separate downtown planning projects.

That’s why city officials won’t include that last set of parcels in their projections, saying those pieces of the puzzle aren’t needed in the short term to build the ballpark.

“Part of the original downtown strategy that sought to build out the full downtown included improvements to Autumn Street,” said City Councilman Pierluigi Oliverio, whose district includes the ballpark site. Residents “may make the assumption that this is some type of subsidy for a future baseball stadium, when it is not.”

In fact, in the report, city planners include options not to build any parking or do any significant road work, and for good reason: The Redevelopment Agency has no money beyond what it has already budgeted through 2015.

And the bulk of that money, $35.6 million, will be needed to secure three more parcels of land just to complete the ballpark footprint, demolish buildings and relocate utilities on the site.

John Weis, the agency’s assistant executive director, said the city and state’s current strapped budgets make it hard to predict when more money might be freed up. If the Planning Commission approves the report, the agency could someday move ahead to obtain more land along the east side of Autumn Street to widen the roadway. But none of the parcels are required for the ballpark, said Weis.

San Jose began buying land for a major league park in 2006, when Oakland A’s owner Lew Wolff said he was considering moving the team. The city completed the environmental review required under state law, but it was put on the shelf when Wolff began looking at a Fremont site.

After residents there protested, Wolff returned to San Jose early last year, and plans for a stadium were revived. Although the environmental report had been signed off in 2007, changes in state law and a mistake in the original traffic analysis forced revisions.

Perhaps the biggest change is that the current plan calls for a ballpark that is smaller and lower in height. The new stadium would seat 32,000 to 36,000, instead of 45,000, and reach a maximum height of 155 feet instead of 235 feet, in order not to disrupt flight paths at nearby Mineta San Jose International Airport.

The report does not estimate costs to the city should it need to buy additional properties for parking or roadwork.

According to the report, three properties near the intersection of San Carlos and South Montgomery streets could be acquired and demolished for road-widening. Two local real-estate experts estimated the land’s value at about $50 per square foot, which comes to at least $1.4 million just for the land. The value of any buildings on the land or the cost to relocate any businesses there would add more to the price tag, they said.

Also potentially in play are eight parcels between Montgomery and Autumn streets, where the report says an eight-story parking garage could be built. The real estate experts said that property is worth about $90 a square foot, which would total at least $6.2 million for the site.

That location could also serve as a garage for the proposed BART extension to downtown San Jose, and costs to build a garage there would likely be shared by the city and the Valley Transportation Authority, said Weis.

But if parking must be built, Weis favors an alternative plan to put a garage on the existing HP Pavilion parking lot. Funding for that structure, he said, could come from the San Jose Sharks or a collaboration between the hockey team and the agency; the agency could issue bonds that would be repaid by parking fees, not taxpayers.

Greg Jamison, chief executive of Silicon Valley Sports & Entertainment, which owns the Sharks and manages the arena where the team plays, said the team is discussing with the city how a parking garage built on the Sharks lot would be paid for. But he insists additional parking must be built in the area to accommodate a possible ballpark, high-speed rail and BART.

The Sharks are critical of the ballpark environmental report, saying it doesn’t address significant traffic and parking problems — especially on days when simultaneous events occur at the Pavilion and the baseball stadium. The report currently recommends no new parking structures be built, citing 13,847 parking spaces that would be available in downtown lots and garages on evenings and weekends.

That scenario, however, is unacceptable to Jamison and other critics.

Without any new parking, the report assumes fans will walk up to three-fourths of a mile from downtown parking lots to an A’s game, something local neighborhood activist Helen Chapman finds absurd.

“Children are not going to walk that far,” she said, nor will older people. Redevelopment officials counter that Sharks fans already make that kind of trek to HP Pavilion.

The report raises other significant issues. Highway 87 and interstates 280, 680 and 880, for example, all would see major traffic increases from the project. Among proposed steps to lessen those impacts are preferential parking for carpoolers, increased parking fees and other measures to encourage public transit use.

None of this will become a reality, however, unless Major League Baseball team owners remove the San Francisco Giants’ territorial claim to Santa Clara County. City leaders hope a decision by Commissioner Bud Selig will happen within months. While Wolff would pay to build the $461 million ballpark, taxpayers must give the team permission to build on city land, and the council must act by late July to place such a measure on the November ballot.

Contact Tracy Seipel at 408-275-0140.

If you”re interested

The San Jose Planning Commission will discuss the Supplemental Environmental Impact Report for the proposed downtown Oakland A”s ﻿baseball stadium at 6:30 tonight in the ﻿City Hall Council Chambers, 200 E. Santa Clara St.